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Refrigerant Flow Through Flexible Short-Tube Orifices



Y Kim, D L. O'Neal, William V. Payne, MD L. Farzad


A series of tests for a R-22/lubricant mixture (1.2 % oil concentration) were performed with two flexible short tube orifices to develop flow data over a range of typical air conditioner operating conditions. One orifice had a modulus of elasticity of 7063 kPa and the other a value of 9860 kPa. Both orifices had identical lengths (14.5 mm), entrance diameters (2.06 mm), and exit diameters (2.46 mm). The tests included both single and two-phase flow conditions at the inlet of the flexible orifice. Upstream pressures were varied from 1179 kPa to 2144 kPa, which corresponded to saturated condensing temperatures of 29.4 to 54.4 C. Experimental results were presented as a function of pressure, subcooling/quality, evaporating pressure, and modulus of elasticity. Mass flow rates were compared with those of a rigid short tube. The flow rate through the flexible orifices was strongly dependent on the condensing pressure, subcooling/quality, and modulus of elasticity of the orifice material. However, the flow rate showed little dependence to the evaporating pressure.An empirical flow model was developed using the experimental data. This flow model was then combined with an air conditioner system simulation model. Results from the model indicated that the flexible orifice provided better flow control than either a rigid orifice or a capillary tube. However, the flow control with the flexible orifice was not as good as with a thermal expansion valve.
Hvac&R Research
No. 2


Elastomer Modulus of Elasticity, Mass Flow Correlation, Short Tube Orifice, System Simulation


Kim, Y. , O'Neal, D. , Payne, W. and Farzad, M. (2002), Refrigerant Flow Through Flexible Short-Tube Orifices, Hvac&R Research, [online], (Accessed July 19, 2024)


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Created March 31, 2002, Updated October 12, 2021